Figure 1. Classic View of Neutrophil Recruitment.

1) In this classical view, neutrophil recruitment is initiated by exposure of macrophages and other innate immune cells to a PAMP or DAMP that induces expression of inflammatory stimuli such as TNF-α or IL-1β. 2, 3) The vascular endothelium expresses chemoattractants and adhesion molecules in response to these proinflammatory stimuli. 4) Neutrophils bind to these adhesion molecules and arrest on the endothelial surface. 5) Upon neutrophil arrest, both endothelial cells and neutrophils undergo intracellular signaling to mediate leukocyte spreading, followed by apical migration and ultimately diapedesis to the site of injury or infection. 6) Neutrophils that enter the tissue space can then play a role in recruitment of a second wave of neutrophils or other leukocyte type through alteration in chemokine production.